Teletypewriter system



Nov. 10, 1942. F H,` HANLEY 2,301,211

TELETYPEWRITER SYSTEM Filed oct. 29, '1941 m'vENToR EZI/Zey s ATTORNEY Patented Nov. l0, 1942 TELETYPEWRITER SYSTEM Frank Harold Hanley, Butler, N. J., assigner to American Telephone and Telegraph Company, a corporation of New York Application October 29, 1941, Serial No. 416,928

2 Claims.

This invention relates to telegraph and teletypewriter systems, and more particularly to round robin systems for telegraph or teletypewriter circuits and apparatus.

There are at present several types of so-called round robin systems in use in which a plurality of teletypewriter stations are interconnected in the form of a ring or loop in such a way that messages may be transmitted from any one of the stations in the system to all of the other stations so that all of the stations including the station transmitting the messages may receive and prepare copies of the messages. Each station is generally connected to the round robin system by three conductors, one being employed for transmitting messages from that station to the other stations of the system, the second for receiving messages trom any one of the stations including the home station, and the third is used for control purposes, i. e. for splitting the circuit between the sending and receiving legs at the central office so that the station may transmit whenever desired over the round robin system.

In accordance with the present invention it is proposed to eliminate the third or control conductor and at the same time enable any station to cut or split the round robin circuit, thereby permitting signals to be sent over the round robin system whenever desired. This may be accomplished in accordance with this invention by the use of an arrangement including a slowrelease relay located at the central oflice, the relay being operated under the control of a key located at the station, the key being connected in series with the sending contacts of the sending apparatus.

Tins invention will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing in which Figure 1 illustrates one `embodiment of the invention applied to a teletypewriter system merely for the purpose of illustration, and Fig. 2 illustrates schematically any form of a repeater system which may be used to connect any teletypewriter station with a central office.

Referring to Fig. 1 of the drawing, there is shown a round robin system for teletypewriter apparatus, the system interconnecting a plurality of stations designated TTYB, TTYc and TTYD, and another station TTYA which may include a central cnice CO. The station TTYA is connected to the central cnice CO by conemanating from any one of the stations, such as TTYB, may be transmitted to all of the other stations, including the central office CO and the station TTYA, so that copies of the messages may be obtained at each of the Various stations including, ci course, station TTYA.

The central office CO includes an east repeating relay ER, a west repeating relay WR and a one-way polar relay PRi'which interconnects the armature of the relay ER with the upper winding ci the relay WR. The interconnecting circuit, however, includes one of the armatures ci a control relay C which may be of the dashpot or mercury type, cr of any suitable slowrelease type. The central office also includes another one-way polar relay PRz, the upper winding of which is in series with one of the conductors El extending to the station TTYA. The upper winding of relay PR1 and the lower winding of relay PR2 are the usual biasing windings for such relays.

The station TTYA includes a receiving relay RR, the winding of which is connected to the other conductor E2 extending between the station TTYA and the central office CO. The armature of relay RR and one of its contacts are connected to the receiving equipment TTYR of a teletypewriter apparatus of well-known type. The station TTYA also includes, in addition to the sending portion TIYs of the teletypewriter, a key K which may be used for cutting or splitting the round robin circuit in such a way as to enable the operator at station TTYA to send messages over the round robin system.

The marking and spacing signals emanating from, for example, station TTYB will traverse the teletypewriter stations TTYc and TTYD and then operate the relay ER at the central ofce CO. The armature of the relay ER will then move between its M and S contacts in accordance with these signals and connect oppositely poled batteries B1 and B2 alternately to the armature of the relay. These oppositely poled voltages are then applied through the main or lower winding of the relay PRi and through the back contact of the inner armature of relay C to the upper winding of the relay WR. Hence the armatures of both relays PRi and WR will be moved between their M and S contacts in accordance with the signals. As the armature of relay PR1 moves between its M and S contacts it connects cppositely pcled batteries B1 and B2 over conductor E2 to the winding of relay RR at station TTYA, thereby operating relay RR at doctors E1 and E2. is is well known, messages 55 station TTYA in accordance with the signals.

The armature of the relay RR will then move between its M and S contacts and hence operate the receiving portion TTYR of the teletypewriter apparatus at station TTYA. This provides copy at station TTYA of the signals emanating from, for example, station TTYB. At the same time the armature of relay WR moves between its M and S contacts, connecting oppositely poled batteries B1 and B2 to the line extending to station TTYB to supply home copy to the latter station. It will be observed, therefore, that with key K open the messages are transmitted over the round robin system and also received at station TTYA.

The key K at station TTYA may then be operated to break the transmission over the round robin system. Upon the closure of key K the upper winding of realy PR2 will be supplied with current from the battery B2 connected to this winding. The armature of relay PR2 will then move from its spacing position at contact S to its marking position at contact M. When this happens, oppositely poled batteries will be connected to the terminals of the winding of relay C, thereby operating relay C. Upon the closure of the left inner make contact of relay C, the marking battery B1 connected to the armature of relay PR2 will then be connected to the upper winding of relay WR and, therefore, hold the armature of relay WR on its marking contact M as long as key K is operated.

It will be observed that upon the operation of relay C'the opening of the back contact of its left inner armature will open the circuit between the lower or main winding or" relay PR1 and the upper winding of relay WR so that relay ER cannot repeat the signals to relay WR as heretofore. The closure of the inner make contact lof the left outer armature of relay C will connect an impedance Z110 to the lower winding of relay PR1. This impedance will properly terminate the main or lower winding of relay PR1. By preventing relay ER from operating relay WR, the break signal is communicated to the other stations,

such as TTYB, of the round robin system, and the operator of any such station will stop sending when he fails to receive his home copy.. The closure of the make contact of the right armature of relay C will also light a. lamp L to indicate to the central ofce operator that the circuit has been cut by the operator at station TTYA.

The operator at station TTY A may then send signals into the round robin system while key K remains closed by operating the sending teletypewriter apparatus T'I'Ys. The marking and spacing signals produced by the transmitting apparatus TTYs will operate the relay PR2, thereby moving its armature between its M and S contacts in accordance with these signals. But as the armature of relay PR2 moves between its two contacts, the relay C, which is very slow to release, will fail to release while such signals are transmitted.

The operation of relay PR2 in accordance with the transmitted signals will correspondingly operate the relay WR, the armature of relay PR2 being connected to the upper winding oi relay WR through the circuit of an impedance Z11 and the left inner armature and make contact of relay C. The relay WR will then repeat the signals into the round robin system of stations TTYB, T'I'Yc and TTYD. As these signals reach the relay ER at the central oice CO, they will operate the relay ER and thereby move its armature between its M and S contacts in accordance with the signals. The armature of relay ER will, therefore, alternately connect oppositely poled batteries E1 and E2 to the winding of relay PR1, which is now terminated by impedance Zio, and relay PR1 will then respond to these signals. As the armature of relay PR1 moves between its M and S contacts, oppositely poled batteries B1 and B2 will be connected to the winding of relay RR at station TTYA over the conductor E2. The relay RR will then repeat the signals to the receiving teletypewriter apparatus TTY?v to provide the home copy.

The relay C is of the slow-release type, as already explained, and may be designed so as not to release on the receipt of a. break signal. As will be understood, a break signal is ordinarily sent to break or stop the transmission from a distant station of the system. Such slow-acting relays are well known to those skilled in the art. However, a relay circuit including condensers and resistances, and including also, if desired, a vacuum tube system may be employed to introduce the necessary slow-release feature.

The addition of the relay C and the apparatus associated therewith at the central omce CO enables sending and receiving service to be extended from the central oiiice to the operator at station TTYA without the usual third or control conductor. The apparatus at the central oice is so connected as to respond to the manipulation of the key K at the station T'I'YA and split the round robin loop at the central cnice so as to enableV the operator at the station TTYA to send signals into the round robin system. The circuit arrangement is very simple and employs a minimum of equipment. The cost of the initial equipment and circuits and their maintenance will be low.

Fig. 2 shows a schematical representation of the apparatus in Fig. l, with the addition of repeaters RP1 and R132, which may be at widely distant points from each other. The repeaters RP1 and RP2 may be, for example, at two difierent cities, and they are interconnected by -a line E3. The repeater RF1 may, however, be located at the central office CO. Repeaters RF1 and RP2 may be of any well-known form, and they may repeat signals from one point to another over the line E3 on a full duplex basis.

After sending from station TTYA has been completed, the key K may be released. The relay C will be released, thereby extinguishing lamp L, but station TTYA will nevertheless receive signals from the round robin system,

It will be understood that while but one central oce and but one station such as TTYA have been shown for illustrative purposes, each of the other round robin stations, such as TTYB, may include a central oilice and an additional station connected to the central oice by two conductors, as alreadyV explained. Moreover, each central oiiice may be connected by similar equipment through separate two-conductor circuits to a plurality of stations.

While this invention has been shown and described in certain particular embodiments merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. In a telegraph system, the combination of a central cnice which is part of a round robin system, a station connected to the central oice by a first line for the transmission of signals and by a second line for the reception of signals, the central oiiice having a receiving relay, a sending relay, a control relay and a polar relay, the polar relay interconnecting the receiving relay and the sending relay through the armature and contacts of the control relay, said station having receiving apparatus responsive to all signals received over said second line, a cutting key, and sending apparatus which may send signals over said iirst line after said key is operated, and means responsive to the operation of said key to operate the control relay for breaking the connection between the sending and receiving relays at the central oiiice, so that signals may be transmitted from said station over said rst line and over the round robin system and then be received over said second line by said receiving apparatus.

2. In a telegraph system, the combination of a central oice which is connected to a plurality of stations to form a round robin system, an additional station connected to the central office by a iirst line for the transmission of signals and by a second line for the reception of signals, the central office having a receiving relay, a sending relay, a polar relay, a control relay, the armature of which connects the armature of the receiving relay to the winding of the sending relay through the Winding of said polar relay, said additional station having sending apparatus, a cutting key connected to said iirst line through said sending apparatus, and receiving apparatus connected to said second line and to the armature of said polar relay, and means responsive to the operation of said key to operate said control relay and thereby break the transmission over said round robin system, signals being transmitted from said additional station over said first line after said key is operated, said transmitted signals being returned over said round robin system and to said receiving apparatus over said second line.

FRANK HAROLD HANLEY. 

